Oxygen indicating apparatus



Feb. 18, 19 58 J. P. STRANGE ,3

' OXYGEN INDICATING APPARATUS Filed March 25, 1954 INVENTOR. JoH/v arm vs:

United States Patent 1 2,823,985 OXYGEN INDICATING APPARATUS John P. Strange, Murrysville, Pa., assignor to Mine Safety Appliances Company, Pittsburgh, Pa., a corporation of Pennsylvania Application March 25, 1954, Serial No. 418,544 1 Claim. (Cl. 23-254) This invention relates to apparatus for indicating the presence of oxygen in a gas, and more particularly to apparatus for use with a continuous gas sample.

It is among the objects of this invention to provide such apparatus which operates with a continuous gas sample, which is suitable when only a trace of oxygen is allowed, which indicates the presence of oxygen whenever more than a predetermined amount is in the gas, and which uses the same indicating medium over and over again.

The preferred embodiment of the invention is illustrated in the accompanying drawing, where the single figure represents a side view of the indicating apparatus, with parts broken away in section.

Referring to the drawing, a continuoustubular passage is formed by any suitable means, such as by a glass tube. The tube has a pair of upright portions or legs 1 and 2 which preferably are parallel and vertical. The upper ends of these legs are connected by a cross arm portion 3 of the tube that is inclined upward from the upper end of leg 1 to the upper end of the other leg 2. The shorter leg has an inlet 4 for gas in its side near its upper end. This leg will be called the supply leg, while the other one will be called the indicating leg. An outlet tube 6 is joined to the top of the indicating leg. This is an outlet for the gas that enters the inlet 4 and flows up through the inclined cross arm of the tube. A sample of gas to be tested is introduced through the inlet from a delivery tube 7, the inlet end of which is higher than its outlet for a purpose that will become evident. The gas is delivered to the inlet of the delivery tube continuously.

In order to indicate the presence of oxygen in the gas flowing through this instrument, the supply and indicating legs of the tube are filled to a level above the gas inlet 4 with ammoniacal cuprous chloride solution 8. As the gas flows through the apparatus a gas lift is produced in the inclined arm 3 of the passage, because the gas entering the liquid in the supply leg will form bubbles that will push slugs 9 of the liquid upward through the inclined arm until the slugs fall into the upper end of the indicating leg and the gas escapes through outlet tube 6. To allow repeated use of the liquid the lower ends of the two legs are joined by a lower cross arm 10, through which the liquid in the indicating leg will slowly flow back to the lower end of the supply leg to balance the column therein. Consequently, the liquid will circulate continuously in the tube.

If as little as .1% oxygen is present in the gas passing through this apparatus it will change the cuprous chloride into cupric chloride as the slugs of liquid are forced through the inclined cross arm of the passage. This change from the cuprous to the cupric form causes the clear chloride to turn blue. The extent of color change will depend on the concentration of oxygen in the gas. When there is only a trace of oxygen present the slugs will be turned a very light blue, but continual circulation of the liquid would cause a progressive darkening of the color unless something were done to stop it. Accordingly, copper, such as copper screen 11 or turnings, is placed in lower cross arm of the passage so that the cupric chloride from indicating leg 2 will flow across it. This copper, by adding copper to the solution, changes it back to the clear cuprous form if only a trace of oxygen is present, which is not objectionable. On the other hand, if more than a. trace is present the blue color of the cupric chloride will deepen and become quite noticeable because the reduction reaction of the copper in the lower cross arm is quite slow when compared with the oxidation reaction which produces the blue color.

Although the color of the liquid in the indicating leg can be observed visually, it is preferred to provide means responsive to changes in the color for indicating the percentage of oxygen in the gas. Thus, an electric lamp 12 may be placed beside the transparent indicating leg, and a photocell 13 placed on the opposite side of the leg. The photocell will respond to the light from the lamp reaching it, which will depend upon how much light can be transmitted through the blue cupric chloride. The photocell can be connected to a meter 14 calibrated for percentages of oxygen in the gas, or it: can be connected to an alarm for indicating when more than a predetermined amount of oxygen is present.

To conserve the ammoniacal cuprous chloride solution 8 in the tube by reducing its evaporation, it is preferred to humidity the entering gas. This can be done conveniently by connecting the inlet end of delivery tube 7 to the upper part of a reservoir 16 containing a suitable liquid 17, such as water or ammonium hydroxide. An inlet tube 18 for the gas extends into the upper part of the reservoir and down to a point near its bottom, so that the entering gas will have to bubble up through the liquid before it can escape from the reservoir through delivery tube 7. This will humidify the gas. To improve the humidifying action, the liquid in the reservoir may be surrounded by an electric heater 19 for raising its temperature.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claim, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

Oxygen indicating apparatus comprising means provided with a continuous tubular passage in the form of an upright supply section and an upright indicating section connected at top and bottom by crossing sections, the supply section having a gas inlet in its side, the top crossing section of the passage being inclined upward from said supply section to said indicating section, said passage being provided with a gas outlet beyond the junction of said inclined crossing section and the indicating section, ammoniacal cuprous chloride solution filling said passage to a level above the gas inlet, means for continuously delivering sampling gas to said inlet to push slugs of said solution upward through said inclined section of the passage from the supply section to the indicating section, whereby oxygen in said gas will react with said solution and change said slugs into cupric chloride so that the solution in said indicating section will appear blue, and copper in the bottom crossing section of said passage for changing the cupric chloride back to cuprous chloride as the circulating solution flows past the copper.

References Cited in the file of this patent UNITED STATES PATENTS 2,047,550 Dely July 14, 1936 2,139,902 Malmgren Dec. 13, 1938 2,328,461 Kienle et a1. Aug. 31, 1943 2,382,381 Calvert et al Aug. 14, 1945 2,417,877 Lewis Mar. 25, 1947 2,421,568 Kurland June 3, 1947 

